The response of Escherichia coli, Bacillus subtilis, and Burkholderia cepacia WZ1 to oxidative stress of exposure to quinclorac

The activity response of the antioxidant enzymes superoxide dismutase, catalase, ATP enzyme activities of Escherichia coli (G-), Bacillus subtilis (G+), and Burkholderia cepacia WZ1 (G-) following exposure to quinclorac was investigated. The bacterial strains were treated with the different concentrations of quinclorac (1.65, 16.5, 33.0, 165.0, 330.0, and 500.0 microg L(-1)). Results obtained indicated that SOD and CAT activities of these bacteria were induced positively and obviously by quinclorac, especially to gram-positive (G+) bacteria treated by lower than 330 microg L(-1) of quinclorac. The inhibition of ATPase in E. coli K12, B. subtilis, and B. cepacia WZ1 appeared stronger with the increase of quinclorac concentration, showing a striking dose response relationship, which can, therefore, be used as an available bioindicator for quinclorac pollution. The concentration of quinclorac applied in this research had significant effects on these three bacteria at the early stage of incubation, but none of which was persistent. Native polyacrylamide gel electrophoresis and activity staining of SOD revealed that quinclorac had effects on isoforms of E. coli and B. subtilis, and on the staining intensities of the isoforms of B. cepacia WZ1. When E. coli K12 was incubated with 330 microg L(-1) of quinclorac, the upper band of the isoforms of SOD tended to become slightly more apparent at 1 h after the quinclorac treatment, but the staining activity was slightly reduced after the prolonged treatment of quinclorac. No such changes of the isoforms of B. cepacia WZ1 was observed.